Remove multitexturing support from GrTextureOp.

This turned out to be an optimization mostly for draws with small device
space areas. Moreover, to be an optimization rather than deoptimization
requires complicated per-GPU tuning where even different devices within
the same architecture require different tuning and tuning is different
between GL and VK.

We've decided to go another direction where we *don't* coalesce draws
but rather make it possible to switch textures quickly from within an
op. This should be a GPU-independent optimization that is also
independent of device space area covered.

Replaces the multitexturing benchmarks with a pair of benchmarks.

composting_images* simulates a layered tile-based compositor.

image_cycle draws tiny images N times each such that they can be
batched. This is to catch a particular possible regression in a
planned change to GrTextureOp where it will use "dynamic state" to
batch across textures. We want to catch a slowdown that might result
from putting draws that use the same texture into the same op but no
longer batching the actual GL level draws and instead using the dynamic
state to "switch" textures between draws.

Change-Id: Ib1cc437525b0b0d56969c30dcb66bb1effb42dc5
Reviewed-on: https://skia-review.googlesource.com/145423
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
8 files changed